#include <iostream>

void func(int a, int) // 在这儿是占位参数
{
    std::cout << "a = " << a << std::endl;
}

void func1(int a, int, int = 90, int c = 100) { // 合理，占位符也可以有默认值，但同时默认参数也要在后面
    std::cout << "a = " << a << std::endl;
    std::cout << "c = " << c << std::endl;
}

int main(int argc, char const *argv[])
{
    int a = 100;
    func(a, 10);

    func1(a, 10, 100);
    return 0;
}
